1. Field of the Invention
This invention relates to a swim fin which is adapted to be mounted onto a foot of a swimmer and which has as its primary object the ability of propelling a swimmer through water and more particularly to a swim fin having a foot receiving portion, which is integral with an elongated flexible fin member having movable tips wherein the swim fin is responsive to movement of a swimmer's foot in a direction of the heel to deflect the flexible fin member toward the foot of a swimmer and which is responsive to a reverse kick force produced in response to a movement of a swimmer's foot in a direction toward the swimmer's toe to deflect the elongated flexible fin member in an opposite direction and to move the movable tips along an arcuate path imparting a snapping action thereto and the combination thereof produces a force which propels a swimmer through the water.
2. Description of the Prior Art
It is well known in the art to form a swim fin for a swimmer from a resilient material wherein the swim fin has a foot shoe portion and a fin portion. Certain of the swim fins having a shoe portion are adapted to have either an open toe or a closed toe type of construction depending on the design of the fin. Also, the design of the fin varies widely from fin to fin depending on the objectives and the design thereof.
For example, U.S. Pat. Nos. 4,083,071 and 3,183,529 each disclose a swim flipper wherein the fin portion is formed of a continuous through channel for the flow of water through the fin as a swimmer moves the fin by foot movement to propel the swimmer through the water. The channels provide a means for reducing back pressure when the fin surface is pushed against water enabling a swimmer to use less force during the kicking stroke.
Reissued U.S. Pat. No. Re. 23,006 and U.S. Pat. No. 2,423,571 disclose swim fins wherein the shoe portion encloses the toes to form a continuous outer upper surface of the fin. The fin disclosed in Reissued U.S. Pat. No. 23,006 has a cross-sectional shoe which discloses that the fin is relatively thin in the center of the web and which terminates in relatively thick raised ridges to define a relatively thick rigid edge of the fin member. U.S. Pat. No. 2,423,571 discloses a fin member which is relatively thick at one edge thereof and which tapers in thickness to a relatively thin edge at the other end thereof. At the center of the fin, the thickness of the fin is less than that of the thick edge and greater than that of the thin edge.
The swim fin disclosed in U.S. Pat. No. 2,423,571 permits the fin to experience undulations or serpentine movements wherein the ends of the fin are displaced in a serpentine oscilatory motion to propel a swimmer.
U.S. Pat. Nos. 3,810,269; 3,422,470; 3,239,857; 3,019,458 and 2,737,668 disclose swim fins wherein the foot receiving portion has an open toe end. In the fin portion of the swimmer's foot fin disclosed in U.S. Pat. No. 3,810,269, a rigid center support and two rigid edge supports are provided to insure that the fin member will be held in a relatively fixed position to resist flexing of the fin member.
U.S. Pat. No. 3,422,470 likewise includes a center rib and two edge ribs to provide stiff structure to prevent and retard movement of the fin member. However, apertures having movable flaps are provided in the interior of the web to reduce the force which must be overcome when produced by a swimmer's leg to overcome the force developed by the water resisting movement of the fin by the action of the movable flap within the apertures permiting a certain portion of the water to pass through the apertures thereby reducing the force required to overcome the interaction between the water and surface of the moving fin member.
U.S. Pat. No. 3,239,857 utilizes the concept of a relatively rigid fin member which includes a central support and two edge supports to prevent the fin member from flexing. In addition, the foot shoe portion of the swim fin includes means for enclosing the ankle of a swimmer and to secure the swim fins around the leg of the user to insure that the fin remains on the swimmer during use.
U.S. Pat. No. 3,019,458 discloses a swim fin having a fin member which slopes away from the foot receiving portion at an angle and wherein the fin member has a relatively thin central section, a thicker end section, center ribs to provide support for the central section and relatively thick raised ridges or edges and support around the edges of the fin member. The center ribs and raised edges retard flexing of the fin member in response to movement of the fin by a swimmer in water. The center ribs and raised end edges essentially prevent the fin member from flexing even though the same is at an angle relative to the foot shoe.
U.S. Pat. No. 2,737,668 discloses a swim fin having an open toe and wherein the fin member sides terminate in upwardly curved edges which are integral with the foot shoe portion providing a curved shaped valley which extends upwardly between the shoe portion and edge of the swim fin. The swim fin is permitted to slightly flex at the end thereof to displace the end of the swim fin through a small arcuate shaped angle relative to the shoe portion in order to produce a propeling motion to a swimmer.